Bike's running incredibly hot

[Nai]

Next dumb question from me!

Still on my Rieju RS2 Pro 125. It has the Yamaha XT (/YBR?) Engine in. Last... Thursday morning I had a bit of a scare as my power started to go up and down on my bike regardless of how far I had my throttle on. One moment I was doing 25, then I shot up to 40, then dropped to 25 again. It stopped happening after about 20-30 seconds. Didn't happen again in... 60ish mile of riding (finished my ride in and out of work Thursday and Friday).

Pulled it out for a wash today, did the usual, muck off all over, hit it with a sponge and water, give it a rinse off. In the manual it says to turn the engine on after a wash for a few minutes, so on goes the motor.

After a couple of minutes of cleaning stuff in the garden next to it I thought I could smell something off. Looked at the bike, thought I saw some smoke (more likely steam!) coming from the engine up through the handlebars. I saw a bit of dirt on the right side of the bikes fairing so grabbed a cloth gave it a wipe, and the moment cloth touched fairing it steamed off. I cant imagine that's meant to be running that hot... I cant remember it running that hot before... Its not long had a service (about 2 weeks ago), I check the oil regularly and it was fine last time I checked.

Assuming that it shouldn't be running that hot, and there is a problem, what should I be looking at / for?

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I am still a biking noob, and if you reply with anything beyond checking chain, oil, or tyres please speak slowly and loudly please. Im sure that will help me! Thankyou!

[Frost]

Air cooled bikes need to be moving in order to keep them cool. They run very hot anyway and will easily boil any small pools of water that collect on top of them.

Your bike losing power and being noticeably hotter isn't a good thing. Check it has the correct amount of oil in it. Don't rely on a sight glass as they can easily become misleading due to an oil tide mark or something.